Premarin is a prescription medication that is a mixture of natural equine (horse) estrogens. As an estrogen medication, it can help with several conditions, such as treating menopausal symptoms, preventing osteoporosis, and reducing the symptoms of certain cancers. Premarin comes in the form of a tablet and is taken once a day. Possible side effects include headaches, joint pain, and vaginal bleeding.

What Is Premarin?

Premarin® (conjugated estrogens) is a prescription medication that contains a mixture of natural estrogen hormones. It is approved for a number of uses, such as:

Who Makes Premarin?

It is made by Wyeth Pharmaceuticals, Inc.

How Does It Work?

During and after menopause, women experience a drop in estrogen levels, as well as a shift in the balance of estrogens that the body produces. Before menopause, the main source of estrogen is produced by the ovaries, and the main type of estrogen produced is known as estradiol. After menopause, the main source of estrogen is androstenedione, which is produced by the adrenal gland and is converted into an estrogen known as estrone. Menopausal symptoms and changes result from both the decrease in estrogen and the shift from estradiol to estrone.

Premarin is a mixture of natural equine (horse) estrogens. It helps to relieve menopausal symptoms by replacing the estrogen that the ovaries no longer produce. Because estrogen helps to keep the bones strong, the decrease in estrogen during menopause causes a significant weakening of the bones, often resulting in osteoporosis. By providing estrogen, Premarin can help prevent these menopause-related bone changes.

Very high doses of Premarin can work to relieve the symptoms of certain cancers, including breast and prostate cancer. For prostate cancer, high doses of the estrogens in Premarin work by suppressing testosterone and other male hormones that "feed" prostate cancer. It is not entirely clear how high doses of Premarin work for breast cancer, as estrogen usually stimulates breast cancer cell growth. Premarin will not cure these types of cancers and should only be used to relieve symptoms when other treatments have failed to treat the cancer adequately.

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